Fluid-pressure motor



July 31, 1928.

E. G. GARTIN FLUID PRESSURE Mo'roa Filed Feb. 20, 1920 Patented July 3l,1928.

` .UNITED P or Free.

@einen o. Gomme or QLAREMONT, New HAMPSHIRE AssIGNoR vfro SULLIVANynncnmnpy 'mneaifzg` 1A compagnon 0F nAsseHUsETrs.

.FLUID-nauseas Moron.

My invention .deletes v1ro fluid .fnreeeafre motors. Y 131e obieot ie 1o:provide e111' Y111.111,11,loyefl 111119 pressure moter- A fergtherlolojeoe vof j1:11- 5 yention iefto peoyiele an improyed rereusf .sive4motor in which lfl11ll111g speed moy be obtained- Another .obieet of..y 1&1- vvolition .is to providean improvediilin prefer sure motor ;ofthe 4,serial-.Y11g-ly,eless type vin which vfluid, dstributonfwill beVrheffeolie@ 1,11

eueh manner es to Proy-ide e irelatinely @1111- -eushioned blow yyhleyet R 'ding @ample luid -for a Iquick and fposiiye return stroke..Fureherobjeete ofmy invention yylll .appear 15 during the descriptionthereof.'

In -the accompanying :drawings I -Shown for purpoeeeoffilloeseizionnooe1112111 Y oyfheh any invention-:may @55eme in meeneelIn these dra'y vings,.-` jFig- -11 Aiis e -`rwew ...teken e neutral looygitodioel iplenekthrough itheioylinder of my motor end feu-111mg the een@rol heee off,the-tool -in whiehfrhe filkuseretziye ef my motor is :embodied `.fleeingof @he 1lype known asa stoper.

Fg- 2 .is a 1Similar fyiew -yeeh .Ra-11.15 .111 .different positions. y

In the illustrative emboilwnt I here `shown a. motor generally 'dieatedby 1 llaving .o Cylinder membe1z2 proyided 51,1991 end reef heedmembers3 enel flfrveepeokyely, therebeingmountedrondelle-renewed ber alehuckhousing v541ml. Qnhegearliegd Ythere is located e throttle :1111111151641i mell- 35 .known AConstrnotion. This @ebree-,11e ,Yelye `Serveeto.voonerol se supply o'le v-iiod .ehloegh 11111410111 37 to the motor-.n"d rfhyooglleportto -t-he feed me linden employed in .stop1ng, flelieAfeed eyln .errnot--bengf-el1ow11 nllesofdeefwinge es it 'is ofwellkoown .-eoaeereoeiom- 1711.111

mdf-Ain v Appueatxo'n tiled iEebrwary 211i 11912.0- 1811111911@ 36.9f157eeyeod1he-yvel1eof the bore .1 2 Ithrough yhieh fluid distribution iseoeomplieh'ed- AnfelQllgd ,11.11.1111 pol-'t 18 communicates ,by Jmeansof. :a longitudinal fluid supply passage 51,7 l,with the port 7 formedin :the `t,l1=x' o tt ,le yalye and Serves toadmit'uid gressnre atlyintesrvals, yas hereinafter deeerbed, ito ,the .bores of 111eoylinder- Com- .gnuniieating with ,the smaller `bore ofi/he `cziylinderagta fpointltoward vthe forward end @160i 1S :e yP01119 1.10111 Whoh arearwardly exeendedpee'eege.2021eede to e port 21 looetled eine extremeroer endof the -oylnder bore 4.19 .12, this .feeeege Serving for 111eSupply-,of-

(tot, e rea-r had 35 ofltlie vreduef-xdpory{tion- 149:1 the Lpieton-Commoniooble with ...the seafood of ffheaoylnder lbore .'12 by moons a,po13t222 ,whieh is'eontrolledby a valve Z9 .23,15 e peeeeeefliexteodiog 1o 111e :forwerd .\-.e11dof'1hele1eer bore ofithe oylnderend opening thereinto vbyIneens` of e Pore '25- .The yelye :2:3 1eprovided with o 4pieton 26 reoiprooeloeio e ehamber 27 and :the ehem-Aber 2 7 ioo 1111r11111-1'oiteeJoy mee-11S :of: ,e 'reeee'ee1281111.11111@ reer .end of ,111e- .lefge eyloder y :here :.11- Ao.exhaust yport .30 ie Provided `,ip-tlm Kvgvalllof Atlieslargeloore 11lof theeylinder snfch position ,as to be `opened by the 5 9 head v llofthe piston-.just before theinstant y,,ofi111raee.1-o.11,1hefor1veedo1roke and o11`1he vrelaryvlfarl ,stroke at a somewhatearlier in- St 11.1 in 111e stroke Cooperating .with the piston .andprojeeliing into the front eri-dof, the feylnder 4is" ,a Striking1.bleek 311 .adopted A1gobes 'rillck pyighe piston at -the endof itsgforwaldnioement. Abt 3,3 lhave indicated `f,eieleeoseafloideupp-lyubeodeiotedtooondiret lelearising fluid to a drill steel 34@ ,Iti-yyill ,be understood .that :the relative position ,kofllepartsmay `-bleVaried in reason in aeeordenee ywith the reqiliremenee of design,,andi-[habille ,preeisepositons shown are not essentiel @oftheIoperation of 111e motor, the onilng 4@1f Lthe parte being Subieet 1oent in ,yarions working-forms ofgthis .feonetruetion- Theolperatidonofihis devieisas follows: 1.Sf'farfingwith '111e Poeeion offthe :Pieton es shoxkavnf-in Fig. 1,1 fluid pressure' supplied under`control ofthe :throttle valve 6 enters ythe pressure .supply passage 17and passing into port 1S, enters the cylinder by means of the annularpassage 16 through which it passes forward tothe large bore 11 of thecylinder. It acts herein on the rear surface of the large head 13 of thepiston, this surface being called hereafter l32. It simultaneouslypasses by wayof port 19, passage 20, and port 21 to the rear end of thesmall bore of the cylinder where it acts on the surface 35 of portion ltof the piston. Fluid pressure also passes Vthrough passage 23 to theupper end of chamber 27 where it acts on the top head of piston 26 andmaintains the valve 23 closed, thereby closing port 22. .From theconstruction il lustrated, it will be seen that at the rear end of thepiston stroke the portion 14V of the piston .overruns by a.' slight`amount the port 22. From the position shown in Fig. 1, the piston moresforward under the action of live pressure until theport A19 is closed bythe forward end of the unreduced portion of part 14 of the piston, andexpansion" begins in the rear end of bore 12 of the cylinder. Port 13nextclosed and the. piston continues its movement entirely under eX-pansive action of ,the fluid Aon surfaces 32 and 35. lWhen the front endof the portion 141 of the piston closes port 19, communication betweenthe surfaces 32 and 35 of the pistonyis shut off and during furthermovement of the piston, the fluid works in the two chambers. separately.Somewhat later in the stroke, the rear end of the portion 14 of thepiston uncovers the rear end of the elongated port 13 and live fluidpressure enters the chamber 12 of the cylinderv bore and builds up apressure therein. When the pressure becomeshigh enough, when acting onthe surface of valve 23 exposedV through port 22 to overcome the reducedpressure in chamber 27, which pressure has beenreduced due to expansion,live pressure will be permitted to pass by way of passageway 24;'andport 25 to the front end of the cylinder. The precise moment of openingof valve 23 may be determined by proper proportioning of port areas andof the piston 26 in such manner `that this valve will open prior toopening of exhaust port 30, or its opening` may be delayed until. evenafter that' event. Owing to the fact that pressure t0 effect thereturnstrole of the piston must pass through the chamber behind theportion 11l of. the piston, in which expansion has greatly reduced thepressure, and .must build up a pressure therein sufficient to open thevalve 2G, which pressure may, `if desired, be less than the inletpressure,r1t will be obvious that fluid pressure will not be ad mittedto the front end of the bore 11 of the cylinder until the stroke of thepiston has been almost completed and that such pressure as is admittedthereto will be' initially less than would be the case were admission tooccur directly to passage 24: and not through the reduced pressurechamber in the lrear L,end of the bore 12. As a result of thisconstruction the piston will strike an almost uncushioned blow on theplug 31. It will be noted that on the return stroke of the piston whichwill occur when the pressure in the forward end of the vbore 11 of thecylinder acting on the full face 36 of the piston overcomes thepressures acting on' thesurfaces 35 and 32, the piston will `movebackwards, closing the eX- haust port 30 and buildingV up a cushionpressure untilthe port 18 is opened.- After theclosur'eof the' port 18by the rear end of the part y141 of the piston, the pressure fluid intherear end of the reduced bore 12 of the cylinder will be forced aroundinto the front end'of the cylinderin a well known manner andwill aid inthe operation ofthe motor. At the moment when the front end of 4port 18is opened, live'pressure will pass into the rear end of the bore 11 ofthe cylinder and will build up therein a pressure in combination withVthe cushion pressuresuflicient to close the valve 23 againstthe pressuretending to hold it open, which pressure will have fallen o both through'expansion in the front 'end of the cylinderV and due Vto the opening ofthe exhaust port 30. Vhether the throwing of this valveshall beaccomplishedby the 'differences in pressuresl in the opposite ends ofthe chamber 11 of the cylinder prior'to exhaust at the front end of thecylinder, or after exhaust has occurred from port 22 may be effectedbefore or after the opening of the front end `of port 18, this beingdetermined by the area of piston 26 'and other factors.V `From theforegoing statements it rwill be seen that a motor is provid-ed inwhicha substantially uncush- -ioned blow may be struck the steel, inwhich kby expansion longitudinally through a reduced space inthecylinder the time of opening of a control valve for one end of thecylinder may be varied, and in which by eX- pansion of'motive fluid fora return stroke through a reduced pressure space, the degree of cushionon the forward stroke may be regulated and reduced. As the matter ofcontrol of the front end of the large cylinder bore is largelyindependent of the posiltion of the front end of port 13, the moment ofcut off on the forward. stroke may beV made later, if desired, thanwould otherwise be possible.

lVhile I have in this applicationspeciically described one form which myinvention vmay assume inpractice, it will be understood that this formof the same is shown for tion may be modified andL embodied in otherforms without ydeparting from its spirit orv the scope of theappendedclaims.

What I claim as new and desire to secure by Letters Patent is:

1. A fluid pressure percussive motor coinprising a cylinder, a pistonreoiprocable therein having a reduced shank, and fluid distributionmeans including ports vand passages for supplying Vmotive fluid to theends of said cylinderto act on both sides -of the piston for effectingreciprocation of said piston one of said passages having only a singlemouth 'or' supply port alternately opened and closed by said shank andoperative to conduct motive fluid to one side `ofl said piston toefl'ect a rearward stroke of the latter, and means normally tending toopen by pressure and held closed bythe motive. fluid at the other sideof said piston to maintain saidpassage closed during a substantialportion of the forward piston stroke.

2. A fluidv pressure motor comprising a cylinder having front and rearends, a piston reciprocable in said cylinder, and fluid distributionmeans for .effecting reciprocationv of said piston including aninletport alternately opened and closed by said piston, passagescommunicable with said port for conducting motive fluid to both ends ofsaid cylinder, and la. valve controlling one of said passages, saidvalve controlled passage being. adapted to `conduct motive fluid fromone end 0f said cylinder to the other end thereof to effect a rearwardstroke of said piston and having communication with each end of saidcylinder at opposite sides ofl said inlet port througha single portonly.

3. A fluid pressure "motor comprising a cylinder having bores of twodiameters, a

piston having a head disposed iii the larger.

bore and a reduced shank disposed in the smaller bore, and fluiddistribution means for supplying motive fluid to the endsy of saidcylinder for effecting reciprocation of said piston including passagesyalternately opened'and closed'by said shank forv directly admittingmotive fluid to the end ofsaid shank and to the portion ofthehead'adjacent ksaid shank, a passage communicating with the smaller borethrough only a single port for conducting motive fluid tothe other sideof said head, and a valve located between the ends of saidlatter passagefor controlling'the flow of fluid therethrough, said latterpassage beingsuccessive-ly controlled by said shank and by said valve.

4. A fluid pressure motor comprising a cylinder having bores of twodiameters, a piston having a headdisposed Ain the larger bore and areduced shank disposed in the smaller bore, and fluid distribution meansfor supplying motive fluid to the ends of said cylinder for effectingvreciprocation of ,mentioned stroke; Y

said piston including means foradmitting live motive fluid to the rearIsurfaces of said piston to act thereon, a passagehaving com- Vmunication with the smaller -bore through a single port onlyand adaptedto conduct motive fluid to t-lie forward end of said cylinder, and avalve forv con-trollingl the flow of fluid through said port,fsaidvvalveA being opened by pressure admitted past the rear end of said shankand being controlled' by the pressure acting'on the-rear surface offsaid pistonhead.

5. A fluid pressure motor' comprising a cylinder .having bores ofv twodiameters, a-

piston having portions disposed in said bores, and fluid distributionmeans for effecting reciprocationof said piston including meansto admitlive motive fluid ,inter-y mittently to bothof said bores at the otherside of said piston to effect a stroke of Sai-d piston in one directionand to one of said bores at therother side of said piston to'y effect astroke ofy said piston in the reverse direction, saidv last mentionedmeans comprisiiig `a passage lia-ving only a single mouth or supplyport, and contro-llingmeans therefor controlled by said piston andthedifferences in pressure of the livefluid aeting in said bores to effectsaid first mentioned stroke. f

6. A fluid pressure motor coiiiprisi-ng a Cylinder having bores of twodiameters, a

piston having a head disposed in the larger bore and a reducedshankdisposedk in the smaller b0re,'a1id vfluid distribution means forsupplying motivefluid to the ends of said cylinder lfor effectingreciprocationof said piston including means intermedi-ate the ends ofthe smaller bore for admitting live motive fluid to the rear surfacesofsaid pistonto act thereon, a passage having coi-nmunication with thesmaller bore through a single port only and adapted to conduct fluid lto the forward end of saidcylinder, and a" valve yfor controlling theflow of fluid through said passage, saidvalve being "moved to openedposition by live motive fluid admitted past the. rear end of saidsli-ank'.

7. A fluid pressure motor comprisingl a cylinder having bores of twodiameters, a pistonj having portions disposed in said bores, yand fluiddistribution meansfor effecting reciprocation of said piston includingmeans to admit motive flu-id intermittently to both of said bores at onesideV of said piston to effect a stroke of' said piston in one directionand to the bore at the other Side of saidy piston to effect the strokeof said piston in the reverse direction, said last mentioned meanscomprising apassage having only a siiliglemouth or supply port, andcontrollingmeans therefor controlled by the differences in pressure ofthe live motive fluidl acting in sai-'d bores toeffect said first Vtoeffect a piston stroke in one direction,

and means controlled by the live motive fluid acting on the pressurearea on said shank and by the pressure acting on said pressure area onsaid head to admit a charge of motive fluid from the smaller bore to theopposite side of said piston head to effect a return stroke.

9. A fluid pressure motor comprising a cylinder, a piston therein havinga pair of pressure areas for operating it in one direc- -tion and asingle pressure area larger than either of said areas for operating itin the opposite direction, and 'fluid distribution means for effectingreciprocation of' said piston including ,means to admit live motivefluid to both of said first mentioned presgsure areas for differentperiods but to neither for a full stroke, and means to admit motivefluid to the last mentioned larger pressure area controlled by livemotive fluid acting on one of said first mentioned` pressure areas. Y y

lO. A fluid pressure motor comprising a cylinder, a piston therein, andfluid distribution means for effecting reciprocation `of said pistonincluding an inlet port, means formed in part on said piston forconducting motive fluid from said inlet port to act on said piston toeffect opposite' movements thereof, whereby at a given point in thepiston stroke the admission of fluid acting to effect onestroke of saidpiston is controlled completely by said piston, and means including avalve for controlling the admission of fluid to effect the oppositestroke of said piston, said valve being controlled by said piston, allofthe fluid effecting said opposite stroke flowing past said valve. l

11. A fluid pressure motor comprising a cylinder, a piston therein, andfluid distribution means for 'effectingreciprocation of said pistonincluding an inlet port, means formed in part on said piston forconducting motive fluid from said inlet port to act on said piston toeffect opposite i movements thereof, whereby at given points in thestroke of said piston the admission and cut off of fluid acting toeffect one movement of said piston is controlled completely by thelatter, and a valve for controlling the admission of' fluid to effectoppositemovement of said piston, said valve being controlled by saidpiston, all of the fluid effecting said opposite stroke flowing pastsaid valve.

12. A fluid pressure motor comprising a cylinder, a piston therein, andfluid distribution means for effecting reciprocation of said pistonincluding fluid inlet and Vconducting passages for eeoting forwardmovement of said piston, said passages being completely closed by saidpiston during movement thereof thereby causing the pressure trapped inthe rear end of said cylinder to expand down to a pressure materiallyless than inlet pressure, means for conducting motive fluid to the frontend of said cylinder longitudinally through the rear end of saidcylinder which contains the reduced pressurewhereby the cushioningaction of said fluid on the forward stroke of said piston may beminimized, and means for maintaining said last mentioned means closedduring a substantial portion of the forward piston stroke.

13. A fluid pressure motor comprising a cylinder having bores of twodiameters, a.

piston having ahead disposed in the larger bore and a shank disposed inthe smaller bore, and fluid distribution means for effectingreciprocation of said piston including means to admit mot-ive fluid tothefseveral pressure areasof said piston comprising a single inlet portcommunicating directly with the smaller bore and alternately opened andclosed by said shank, a plurality of fluid distributing passages,atleast one of said passages being controlled completely by lsaidpiston, and a valve for controlling at least one other of said passages.

14. A fluid pressure motor comprising a cylinder having bores of twodiameters, a piston having a head disposed in the larger bore anda shankdisposed in the smaller bore, and fluid distribution means for effectingreciprocation of saidpi-ston including means to admit motive fluidintermittently to the several pressure areas of said piston comprising asingle inlet port communicating with the smaller cylinder bore, aplurality of passages one of which being controlled completely by saidpiston, and a valve for controlling another of said passages.

15. A fluid pressure motor, a cylinder having communicating bores of twodiameters, a piston in said cylinder having a head disposed in thelarger ofsaid bores and a shank disposed in the smaller thereof',` andfluid distribution means for effecting reciprocation of said pistonincluding means for supplying live motive fluid to each of said bores atone side of said piston for only a part of the piston stroke to effectsaid stroke in one direction and to the bore at theother side of thepiston to effect a return stroke of said piston, anda valve forcontrolling said supply means for effecting one of said strokes of saidpiston.

16. A fluid pressure motor comprising a cylinder havingcommunicatingbores of two diameters, a piston in said cylinder having alll Y passage communicating with the smallerH inlet port alternatelyopened and closed by said shank, means forsupplying motive fluid to theen d yofsaid Vshankand to the portion of the h ead adjacent said shankfor effecting one stroke of said piston, a passage for' supplying fluid'to the other side of. said head to effect a return stroke of saidpiston,

said passage communicating with the smaller bore adjacent therear endthereof, and a valve for controlling Asaid passage.

cylinder having communicating bores of two diameters, a piston in saidcylinderhaving a head disposed in the larger (bore and a' shank disposedinthe smaller boi-e, and fluid distribution means for effectingreciprocation ofv said pistonincluding a single inlet 'i portalternately opened and closed by said shank, means for supplying motive`fluid to the end of' saidv shank and to the portion of said headadjacent said shankforeflecting one stroke of said piston," a passagefor sup, plying fluid to the other side of said head to effect a returnstroke of said piston, lsaid bore adjacentfthe rear end thereof, and avalve controlling the communication of saidv latter passage with saidbore.

18. A fluid pressure motor comprising a cylinder having a plurality ofcommunicatingl bores of different diameters, a piston having a headdisposed in the larger bore anda shank disposedin the smaller bore, andfluid distribution means for effecting reciprocation of said pistonincluding a source of motive fluid supply, means for 'supplying motivefluid to both of said bores atone side of said piston to effec-t forwardstroke of said piston, means for supplying motive fluid through saidsmaller bore to said large bore at the other side of said piston toeffect the return stroke of said piston, a valve controlling said lastmentioned fluid supply means, and means for maintaining said valve inits opened position for al period after communi-` cation between saidsource of motive fluid supply and said second mentioned means isinterrupted.

19. A fluid pressure motor comprising a cylinder having front and rearends, a piston in said cylinder, and fluid distribution means forsupplying motive fluid to the ends of said cylinder for effectingreciprocation of said piston including an inlet port through whichmotive fluid for both ends is supplied alternately opened and closed bysaid piston, a passage having only a single mouth supply port overrun bysaid piston and adapted when in communication with said inlet port toconduct motive fluid to one end of said cylinder to effect one stroke of11A fluid pressuremotor comprising a` said piston, and means controlledby the motive fluidi in the otherend ofA saidv cylinder to maintain saidpassage' closed during` a substantialportion of the other piston stroke-20. A fluid pressure motor comprising a cylinder having a largev forwardbore and a reduced rearward bore, a piston in said cylinder having ahead disposed in said large bore andi a reduced shank disposed in saidreduced bore, and yfluid distribution means, for

supplying motive fluid to said" cylinder to effect reciprocation of saidpiston including a/fluid inlet port communicating ,with v said reducedboreV and alternately openedv and closedby said shank, a passage havingonly a single mouth communicating with said reduced bore and operativeto conduct motive fluid' to the forward end of said large bore to effectrearward stroke of said piston, a fluid conductingv groove formed onsaid shank for conducting motive fluidv toA the rear end of said largebore, a passage controlled by ,said Vshank for connecting said groovewith the rear end 4of said reduced Y b ore, a valve forcontrollingthe'flow of' inotive fluid through said first mentioned pas-"sage, and a passage constantly communicating at the rear end of saidlarge bore and vwith said valveA for maintaining the latter in itsclosed position during a substantial portion `of the forward pistonstroke.

2l. A fluid pressure motor comprising af cylinder having bores of twodiameters, a piston therein having ahead disposed in the large-r boreand a shank disposed in the vsmaller bore, and fluid distribution'meansfor effecting reciprocation of said piston comprising means for causingexpansive action'of the pressure fluid in the smaller bore during theforward piston stroke, means for admitting pressure fluid through thesmaller bore to the forward end of said cylinder, and means formaintaining saidlast mentioned means closed 4during a substantialportion of the forward piston stroke and for opening said means prior tothe completion of said stroke.

22. A fluid pressure motor comprising a cylinder having communicatingbores of two diameters, a piston having a head 'disposed in the largebore and the reduced shank disposed in the small bore, and fluiddistribution means for effecting reciprocation of said piston comprisinga fluid inlet, a passage for yconnecting said small bore with said largebore, a passage opening into one end of said small bore, said shankbeing adapted to connect said small bore and the rear end of said largebore by way of said last mentioned passage, said piston being movable inopposite positions to place either of said passages in communicationwith said inlet while closing the other of said passages, and means formaintaining said first mentioned passage closed 'during' a substan tialportion of the forward piston stroke.

23. A fluid pressure motor comprising a cylinder having communicatingbores of different diameters, a piston having a head disposed in thelarge bore and a reduced shank disposed in the smaller bore, and fluiddistribution means for eecting reciprocation of said piston comprisingconduit means communicating with said small bore and adapted to admitfluid to the rear end of said large bore to act on the rear surface Vofsaid piston head, a fluid inlet communicatingwith said small bore andadapted to admitfluid to the rear end of said large bore whencommunication between said inlet and said small bore is closed, aconduit for conducting fluid from said inlet to the forward end of saidlarge bore, and a valve controlled by the pressure at the rear side ofsaid piston head for maintaining said latter passage closed during asubstantial portion of the forward piston stroke. y

24. A fluid pressure motor comprising a cylinder having front and rearends, a piston reciprocable in said cylinder having an enlarged head anda reduced shank, and

i fluid distribution means for effecting reciprocation of said pistonincluding a fluid inlet port, means including passages for conductingfluid to the opposite ends of said cylinder to act on the pressure areason said head and said shank, said passages and said inlet port beingalternately connected and Yinterrupted by said shank, and means formaintaining the passage connecting the inlet with the forward en'd ofsaid cylinder closed during a substantial portion of the forward pistonstroke. i

25. A fluid pressure motor comprising a cylinder having front and rearends, a piston reciproeable in said cylinder having an enlarged head anda reduced shank and fluid distribution means for effecting reciprocationof said piston including a fluid inlet port, means including passagesfor conducting fluid therefrom to the opposite ends of said cylinder toact on the pressure areas on said head and shank, said conducting meansand said inlet port being alternately connected and interrupted by saidreduced shank, and a valve for controlling flow of fluid through one ofsaid fluid conducting passages.

26. A fluid pressure motor comprising a cylinder having communicatingbores of different diameters, a piston therein having a headdisposed inthe large bore and a ree duced shank disposed in the small bore, andfluid distribution meansfor eecting reciprocation of said pistonincluding a fluid nlet port, passages for conducting fluid ther from tothe bores of said cylinder, said conducting means and said inlet portbeing alternately connected and interrupted by said shank, the pressurefluid expanding in passing through said smaller portion of the bore toone of said passages, and a valve in said latter passage for maintainingthe same closed during a substantial portion of the forward pistonstroke.

In testimony whereof I aflix my signature.

`ELMER G. GARTIN.

CERTIFICATE OF CORRECTION.

Patent No. 1,679,128. Granted July 31, 1928, to

ELMER G. GARTIN.

It is hereby certified thaterror appears in the printed speoification ofthe above numbered patent requiring' correction as follows: Page 3, line14, claim -l, after the syllable "ton" insert a comma; same page, line84, strike out thel words "the other" and insert instead the Word "one";and that the said Letters Patent should be read with these eorrectionsltherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 25th day of September, A. D. 1928.

M. J. Moore, (Seal) Acting Commissioner of Patents.

